This invention relates to the leaching of refractory gold ores.
It is a well known phenomenon that when gold ores are leached with the usual additions of lime that are made to cyanide solutions, the extraction rate is adversely affected by the presence of sulphide minerals of arsenic and antimony as well as base metal cyanicides such as Ni, Cu and Co. It is also known that if the pH of the leach solution is reduced to levels as low as 10, the extraction rate can be increased. However, in order to attain satisfactory recoveries of gold even when leaching at these low pH values, the leaching times may sometimes be inordinately protracted.
The term "ore" is intended to mean not only ores as mined but also dumps, tailings, concentrates and other products emanating from mining operations.
It is an object of the invention to provide a process in which the gold from such a refractory ore could be dissolved, in acceptably short leaching times, with higher recoveries of gold than can be obtained using conventional procedures, for example, those used on the Witwatersrand, South Africa.